Turbine Stator Blade Research Articles

Reaction mechanisms and mechanical properties of SiCf/SiC composite and GH536 superalloy joints using CoFeNiCrMn high-entropy alloy filler

To meet the service conditions and strength requirements of turbine stator blades and the inner and outer rings of aero engine casings, CoFeNiCrMn high-entropy alloy filler was used to braze SiCf/SiC/GH536 joints. This study investigated the effects of holding time on the joints' microstructure and mechanical properties. Key phases identified in the welded joints include MoNiSi, FCC, and Cr23C6 near the composites, with brittle Ni3Si and Fe2Si intermetallic compounds forming due to filler diffusion. Optimal brazing parameters were found to be 1220 °C for 30 min with a shear strength of 64.28 MPa. The study also highlighted that increased holding time at the same temperature enhances diffusion at the joint, increasing brittle intermetallic compounds, initially improving shear strength, which then declines. Microstructural and fracture morphology analyses revealed that insufficient insulation time leads to poor welding and stress concentration at pores, causing cracks. Excessive insulation time results in joint fractures due to the brittleness of Ni3Si and Fe2Si intermetallic. Thus, joint shear strength correlates with welding quality and intermetallic compound distribution.

Numerical study on cooling performance and thermal stress characteristic of an f-class gas turbine stator blade

In this study, a coupled numerical computation approach integrating aerothermal and thermomechanical effects was employed to investigate the cooling efficiency and thermal stress characteristics of gas turbine stator blades. A comprehensive analysis was conducted considering varying turbulence intensities in the coolant flow (spanning from 0.05 to 0.15) and different coolant media configurations, including pure air, dual-medium mixture of air and steam, and pure steam. The distributional traits of cooling efficiency and thermal stress on the stator blade surface under these conditions were meticulously examined. Furthermore, quantitative assessments were performed to determine the extentto which coolant turbulence intensity and coolant type affect the average cooling efficiency and maximum equivalent thermal stress of turbine stator blades, thereby revealing the influence laws. The results reveal that the minimum cooling efficiency on the stator blade surface predominantly occurs at the position of channel 4 on the pressure surface, while the highest cooling efficiency is generally found near the leading edge of the suction surface. Regions of elevated thermal stress were consistently concentrated around the stator blade tip and root areas. When the coolant turbulence intensity increased from 0.05 to 0.15, the average cooling efficiency on the stator blade surface improved by 2.06%, accompanied by a reduction of 1.12% in the maximum thermal stress. In comparison to pure air cooling, dual-medium (air and steam) cooling and pure steam cooling lead to respective enhancements in the average cooling efficiency of approximately 3.3% and 13.2%, with corresponding decreases in the maximum thermal stress of 2.18% and 10.2%.

Structural Integrity of Turbine Stator Blades Using Different Super Alloys with Internal Cooling at Fluid Temperature Range of 600 K – 700 K

The importance of turbines in power generation cannot be overstated. While the failure in stationary plants can lead to downtime and high repair costs, its failure in mobile plants like the jet engines can be catastrophic with attendant loss of lives. Hence, by all possible means, the prevention of turbine failure is a necessity, and a very good means of doing this is with the use of super-alloys. Super-alloys are tailored to withstand the demands of turbine operations especially stress and elevated temperature and pressure. The blades are thus, manufactured from super-alloys, and of prominence are the Nickel-based super-alloys. The performance of five different super-alloys: (DS) GTD 111, Ti-6Al-4V, Inconel 718, CMSX-4, and Nimonic 80A was simulated using COMSOL MultiPhysics 5.5 at cooling air temperature range of 600 K – 700 K. The mode of cooling employed in the study is only internal cooling. With the developed stress percentage of the yield stress value and the stator blade displacement at the operating conditions as the criteria of performance, super-alloy Ti-6Al-4V faired as the best material for the stator blade.

Numerical study on the interaction between rotating detonation wave and turbine stator blades with multicomponent mixtures

Aiming at the coupling problem between rotating detonation combustor and turbine components, this paper uses methane recuperation gas as fuel and adopts two-dimensional numerical simulation to study the working process after coupling between rotating detonation combustor and turbine stator blades. The results show that with the increase of methane conversion, the propagation mode changes from single wave mode to unstable single wave mode. Under the two modes, after the oblique shock wave sweep, the turbine stator blade outlet Mach number suddenly rises to 2.5. In addition, the flow field structure of a single turbine blade is also analyzed, and it is found that after oblique shock wave sweep, the flow field structure changes, and boundary layer separation occurs at the trailing edge of turbine stator blades. Turbine stator blades have a certain inhibition effect on the pressure oscillation at the combustion chamber outlet, and the disturbance generated by detonation wave extinguishing in unstable single-wave mode will be transmitted through turbine stator blades to the outlet. With the increase of fuel activity, turbine stator blade pressure loss gradually increases. The total pressure loss coefficient of single-wave mode is 9%, and the total pressure loss coefficient of unstable single-wave mode is 4%–6% higher than that of single-wave mode.

Impact of Cooling Fluid Temperature on the Structural Integrity of Gas Turbine Stator Blades

The importance of gas turbine engines to the aviation industry cannot be overemphasized. Being a major part of aircrafts and jets, its reliability must be second to none. They are continuously subjected to extreme conditions during service making them the subject of constant studies. To produce the thrust and torque power required of them, they have to convert the intense heat and pressure inherent in hot combustion gases. To withstand the high combustion gas temperature without thermal failure, specialized materials and cooling are employed. This study numerically investigated the effect of cooling fluid temperature on the structural integrity of a (DS) GTD111 alloy gas turbine stator blade using COMSOL 5.5 software. Air was used as the cooling fluid in this study. The duct passages of the stator blade are significantly affected by the cooling fluid temperature values. Lower values of cooling fluid temperature proved beneficial for keeping the stator blade material below its metallurgical limit and is a positive for its total displacement, it however, negatively affects the yielding of the material. The cooling fluid temperature can be optimally selected to give optimal cooling effects in terms of total displacement and stress development. Based on this study, a cooling fluid (air) temperature of about 660 K will give optimal results. Internal cooling alone is not sufficient to produce the required cooling for turbine stator blades and this is evident in the output of the study, thus, coating and film cooling must be carried out to prevent thermal failure during service.

Numerical investigation on the interactions between rotating detonation wave complex and planar turbine cascade

AbstractDue to pressure gain characteristics, the rotating detonation combustor (RDC) can be integrated into gas turbines by further improving the system's performance. The matching of unsteady flows in the RDC and turbine is a key challenge. Here, interactions in an RDC and planar turbine cascade are investigated using the unsteady Reynolds time‐averaged Navier‐Stokes method. The effects of the blade profiles on interactions between the oblique shock wave (OSW) and turbine cascade are analyzed, and the suppression effect of the turbine cascade on high‐frequency pressure oscillations is evaluated. The results show that the OSW interacts with the leading edge, pressure side, suction side, and trailing edge of the turbine stator and rotor blades, which generates complex wave systems in the cascade passage. The opposite propagation direction causes the OSW to be aligned or misaligned with the stator blade. The position of the OSW that operates on the turbine cascade changes, and two different wave system structures appear. The various pitches of the turbine cascade at different blade heights cause differing intensities and propagation directions in the reflected wave as generated by the action of the OSW and turbine cascade and the variable flow fields at different blade heights. The turbine cascade can significantly suppress the high‐frequency pressure oscillations, while the pressure amplitude attenuation rate can reach over 80% when the OSW propagates through the turbine cascade. These findings expound on the interaction mechanism between the rotating detonation wave complex and the turbine stator and rotor blades.

Development of High-Temperature Wire-Grid Thin Film Strain Gauges.

Aero-engine turbine stator blades are often used in harsh environments with high temperatures and high pressure and are prone to fatigue fractures. Real-time and accurate monitoring of blade surface stress and strain is critical to ensure safe operation. In this study, thin-film strain gauges (TFSGs) that can be used in high-temperature environments above 1000 °C were designed and fabricated using a PtRh6 thin film as the sensitive material. The hysteresis effect of the stress transfer upon establishing a thermo-mechanical coupling finite element model of the Inconel718 high-temperature nickel-based alloy equal-strength beam PtRh6 TFSGs was analyzed and the optimal combination of thin-film thickness and longitudinal grid length of wire-grid TFSGs was determined. In order to solve the problem of high-temperature insulation, the insulating properties of a single-layer Al2O3 insulating film, a single-layer ZrO2 insulating film, a double-layer Al2O3/ZrO2 composite insulating film, and a four-layer Al2O3/ZrO2/Al2O3/ZrO2 composite insulating film at high temperature were compared and studied using scanning electron microscopy to analyze the microscopic morphology and composition of the four insulating film structures. The results showed that the four-layer Al2O3/ZrO2/Al2O3/ZrO2 composite insulating film had the best insulating properties at high temperatures. On this basis, an Al2O3/ZrO2/Al2O3/ZrO2 composite insulating film, PtRh6 sensitive layer, and Al2O3 protective film were sequentially deposited on a high-temperature nickel-based alloy equal-strength beam using DC pulsed magnetron sputtering technology to obtain an Inconel718 high-temperature nickel-based alloy equal-strength beam PtRh6 TFSG. Its gauge factor (GF) and temperature coefficient of resistance (TCR) were calibrated, and the results showed that the sensor could be used in harsh environments of 1000 °C. The above results provide new ideas for measuring stress and strain in aerospace under high-temperature and high-pressure environments.

Application of quadratic regression orthogonal design to optimization surface heating for control wet steam condensation flow in nozzle

The condensed flow of wet steam in the low-pressure cylinder of a steam turbine will affect the safety and economy of the unit's operation. Therefore, it is necessary to reduce the influence of the wet steam on the turbine blades after condensation. Based on the research status at home and abroad, in view of the similarity of the steam turbine stationary blade cascade channel structure to the Laval nozzle, taking the Moses and Stein nozzle as the research object. The distribution law of the wetness and other parameters are obtained by numerical simulation under different heating intervals and heating rates. The results show that in the same heating interval, as the heating rate increases, the Wilson point continues to move backwards, while this requires a lot of heating. At the same heating rate, as the heating interval increases, the wetness of the same point also decreases. The maximum heating interval is 50% of the axial length. Finally, through the quadratic regression orthogonal design, the heating parameters to prevent the deposition of droplets on the surface were given, the optimal heating starting point is 1.33 cm, the heating interval length is 5.17 cm, and the heating rate is 0.221669J/(mm2·s). The research results can provide reference for the design of steam turbine stator blade heating and dehumidification.

Optimization of the Trailing Edge Inclination of Wet Steam Turbine Stator Blade Towards the Losses Reduction

Optimization of the Trailing Edge Inclination of Wet Steam Turbine Stator Blade Towards the Losses Reduction

Aerodynamic design and optimization of blade end wall profile of turbomachinery based on series convolutional neural network

End wall contraction is an effective approach to reduce the substantial secondary loss in the cascade with low aspect ratio. This paper proposed a series convolutional neural network architecture (SCNN) to improve the design optimization problem of end wall profile of a turbine stator blade. The specific implementation of the architecture is discussed in detail. The effect of the train size and sensitivity analysis of design variables are carried out. Finally, the optimization is completed by the gradient descent method, and the aerodynamic performance of end wall profile before and after optimization is compared. It shows that the SCNN architecture performs outstandingly with 30% training data. It can quickly and accurately provide rich flow field information and performance parameters within 3 ms after training. When the train size is 0.3, the mean prediction errors of mass flow rate and efficiency of each sample are lower than 0.1%, which performs significantly better than the Artificial Neural Network and Gaussian Process Regression model. When the stator blade adopts optimized contracted end wall profile, the power and efficiency are raised by 4.43% and 1.39% respectively with the mass flow rate only changing by 1.48%, which verifies the feasibility of the SCNN architecture.

Simulation of temperature distribution in gas turbine stator blade subjected to different internal coolant gases

Simulation of temperature distribution in gas turbine stator blade subjected to different internal coolant gases

Numerical investigation of truncated-root rib on heat transfer performance of internal cooling turbine blades

Due to the great heat obtained from the combustion chamber, the turbine blades of a jet engine always operate at high temperatures. Therefore, to minimize the temperature of the turbine rotor and stator blades, the internal cooling system was developed. The original rib called the squared-rib has been developed as a turbulence generator to enhance heat transfer ability. This technique is to cast ribs in the serpentine passage inside the turbine blades. By this technique, the vortex exists in the rear rib region that causes a low heat transfer zone. In this investigation, a new rib configuration called the truncated-root rib was designed to reduce the squared-rib disadvantage. The configuration of the truncated-root rib forms a small extra-passage into which the coolant passes through and the vortex is comparatively removed. To investigate the heat transfer performance and fluid flow characteristic of the internal cooling turbine blades, a parametric study of the truncated-root rib with the height and shapes of the extra-passage was performed using three-dimensional Reynolds-averaged Navier–Stokes equations with the shear stress transport turbulence model. The numerical results showed that all the heat transfer performance of the truncated-root rib configuration is greater than that of the squared-rib. The Nusselt number in the case of the truncated-root rib increases by 8.56% with the Reynolds number of 37 392, and the thermal performance is 39.24% higher than that of the original shape in the case with Reynolds number 53 697.

Performance Investigation of Simple Low-dissipation AUSM (SLAU) Scheme in Modeling of 2-D Inviscid Flow in Steam Turbine Cascade Blades

This study evaluates the performance of the SLAU, AUSM+UP upwind schemes, and CUSP artificial dissipation scheme for the flow through the convergent-divergent nozzles and turbine stator blades under different pressure ratios by developing an in-house code. By comparing the results with analytical and experimental results, it is found that, despite the simplicity of the SLAU scheme in the absence of tuning variables, it provides reasonable predictions for different turbine blades in point of location and strength of the shocks. The SLAU scheme could converge at a much higher rate, leading to very much lower values of residuals. The SLAU scheme causes about 30% and 20% improvements over the prediction of the shock-induced losses in supersonic and subsonic outlet flows, respectively.

Structural and Aerodynamical Parametric Study of Truss-Core Gas Turbine Rotor Blade

Improvement of turbine blades is currently the prime area of research dedicated to the development of more efficient gas turbines. This study examines the structural performance of the gas turbine rotor and stator blades with the implementation of Kagome truss-core structure as inner topology. The truss-core structure was hypothesised to improve the stress behaviour of the blade by reducing the mass and, hence, the centrifugal force induced by rotation, while remaining robust enough to withstand bending stress induced by the flow. In order to analyse the stress state of the truss-core model, fluid flow analysis of transonic turbomachinery was performed via the Frozen Rotor technique in ANSYS CFX and then coupled with ANSYS Mechanical. As a result, the combined surface load of the rotor was obtained and used to estimate the structural performance. By examining the obtained complex stress state of the rotor blades, the truss-core density-dependent structural performance was derived for the given initial and boundary conditions.

Theoretical and Experimental Investigation of a 34 Watt Radial-Inflow Steam Turbine With Partial Admission

Abstract A microsteam turbine with a tip diameter of 15 mm was designed and experimentally characterized. At the nominal mass flow rate and total-to-total pressure ratio of 2.3 kg h−1 and 2, respectively, the turbine yields a power of 34 W and a total-to-static isentropic efficiency of 37%. The steam turbine is conceived as a radial-inflow, low-reaction (15%), and partial admission (21%) machine. Since the steam is limited in the system (solid oxide fuel cell), a low-reaction and high-power-density design is preferred. The partial-admission design allows for reduced losses: The turbine rotor and stator blades are prismatic, have a radial chord length of 1 mm and a height of 0.59 mm. Since the relative rotor blade tip clearance (0.24) is high, the blade tip leakage losses are significant. Considering a fixed steam supply, this design allows to increase the blade height, and thus reducing the losses. The steam turbine drives a fan, which operates at low Mach numbers. The rotor is supported on dynamic steam-lubricated bearings; the nominal rotational speed is 175 krpm. A numerical simulation of the steam turbine is in good agreement with the experimental results. Furthermore, a novel test rig setup, featuring extremely thin thermocouples (ø0.15 mm) is investigated for an operation with ambient and hot air at 220 °C. Conventional zero- and one-dimensional predesign models correlate well with the experimental results, despite the small size of the turbine blades.

An experimental study of the integral characteristics of the intrachannel liquid film suction in a turbine stator blades cascade

This paper presents the results of an experimental study of the integral characteristics of the intrachannel liquid film suction in a flat cascade of turbine stator blades. Two slots for removing the liquid film from the interblade channel were arranged on the pressure surface of the stator blade. The experiments were carried out with initial steam wetness y 0 = 3 ÷ 9.5 % and theoretical Mach number downstream the cascade M lt = 0.6 ÷ 0.78. The operation mode of the moisture removal system was determined by the relative pressure drop on the moisture-removing slots and varied over a wide range. The investigations were carried out for both the operation of the moisture-removing slots one at a time and the combined suction of the liquid film simultaneously through both slots. The measurement system used in the experiments allowed separately determining the mass flow rates of steam and liquid removed from the interblade channel. The obtained integral characteristics served to evaluate the influence of various factors on the efficiency of the intrachannel moisture removal system. Based on the analysis of the research results, recommendations on the design and operation of intrachannel moisture removal systems have been formulated.

Standard module hydraulic technology: A novel geometrical design methodology and analysis for a low-head hydraulic turbine system, part II: Turbine stator-blade and runner-blade geometry, and off-design considerations

Low-head hydropower has the potential to generate a significant amount of electricity from rivers that traditionally were unsuitable for developing hydraulic power plants. To effectively and eco-friendly utilizing those renewable energy resources, a Standard Modular Hydropower Technology was proposed by the U.S. Department of Energy (DOE) in 2017. This new concept offers a new paradigm for small hydropower technology development based on the premise of standardization, modularity, and preservation of stream functionality. This technology has three primary modules: Generation Module, Passage Modules, Foundation Modules , and this series of papers presents a general design methodology for the generation module. The first part of this series of papers covered the basic development of the design methodology and some fundamental geometrical considerations. This second part of the papers presents additional numerical simulation contents on several blade configurations, including stator blade inlet angle, runner blade solidity, and runner blade thickness considerations, and how those geometrical configurations affect the overall performance and fluid behaviors. Additionally, how those geometrical configurations influence the overall off-design performance is also investigated with comprehensive performance maps analysis. With improved blade geometrical configurations, the test models have a vast off-design potential with 23%-1220% operating range and over 75% hydraulic efficiency.

Thermo-mechanical simulation of ultrahigh temperature ceramic composites as alternative materials for gas turbine stator blades

The efficiency of the Bryton cycle strongly depends on the maximum temperature of the cycle. However, restrictions on metallurgical problems deprive engineers from the benefit of high temperatures. Ultrahigh temperature ceramics can be considered in such cases, instead of traditional materials like M152 superalloy. In this study, SiC reinforced HfB2 and ZrB2 ultrahigh temperature ceramics were proposed as gas turbine stator blades. The heat transfer and stress-strain equations were solved numerically by the finite element method to obtain temperature and stress distributions. The results showed that the maximum thermal stress occurs in vicinity of the cooling ducts where the temperature gradient is maximum. The maximum displacements of 1.2 mm (for HfB2–SiC) and 1.14 mm (for ZrB2–SiC) occur in the upper wall. It can be noticed that the ZrB2–SiC made blade showed lower maximum stress and displacement than those for the HfB2–SiC made one, as a result of lower expansion coefficient of ZrB2–SiC system. The addition of SiC to monolithic HfB2 and ZrB2 ceramics decreases their thermal conductivity and following that, the temperature uniformity in blades reduces. Although the thermal stresses and the probability of failure in these stator blades enhance, the ZrB2–SiC material presented the best performance among the other investigated samples. Both Coulomb-Mohr and Von Mises failure analyses were employed. It was understood that both blades made of HfB2–SiC and ZrB2–SiC composites simply withstand the applied stresses with the safety factors of about 1.5.

A numerical approach to the heat transfer and thermal stress in a gas turbine stator blade made of HfB2

Conventional gas turbine blades often face corrosion and oxidation at high temperatures. For resolving these problems, another way in addition to the cooling ducts is selecting appropriate materials for the fragments manufacturing. The present work offers a solution to reduce the metallurgical issues at higher temperatures by using ultra-high temperature ceramics. Despite the rotor blades, stator ones are exposed to hot fluid without any rotation and consequence centrifugal forces. Because brittle materials such as ordinary ceramics are not applicable in the case of high tension forces, hafnium diboride is selected to examine its feasibility for the fabrication of gas turbine stator blades. Thermal stress and deformation of gas turbine stator blades are investigated numerically. Comsol Multiphysics software, utilizing Finite Element Method, was used to analyze the heat transfer and possibility of failure in the stator blades. HfB2 can be a resistant alternative for manufacturing the turbine blades, which does not fail against the applied compressive stresses according to both Von Mises and Coulomb-Mohr theories. In addition, a comparison study between HfB2 and two other diboride ceramics, ZrB2 and TiB2, is conducted.

Heat transfer, thermal stress and failure analyses in a TiB2 gas turbine stator blade

Abstract Gas turbine stator blades do not experience centrifugal force contrary to the rotor blades; but they are exposed to high–temperature combustion gases causing thermal stresses. In the present work, a series of numerical simulations were carried out to clarify the feasibility of TiB2 utilization as an appropriate material for gas turbine stator blades. The governing equations of heat transfer and solid mechanics were discretized by the finite element method and solved using Comsol Multiphysics software. The boundary conditions were applied, and temperature, displacement and maximum principle stress were obtained. The results showed that using ceramics such as TiB2 instead of conventional alloys can enhance the maximum displacement. Temperature distribution in the blade is more uniform than that of alloys, and consequently, the thermal stresses are reduced. The TiB2 can withstand the applied stresses according to the Coulomb–Mohr theory with a safety factor of 2.4.